This invention relates to electrochemical cells. More particularly, it is concerned with electrochemical cells having wound electrode structures.
A particularly effective class of primary electrochemical cells which employs soluble or liquid cathode materials, as opposed to more conventional solid cathodes, has undergone rapid development in recent years. In these cells the active cathode material is usually a fluid solvent for an electrolyte solute which provides conductivity. The active anode of the cell is usually lithium or other highly electropositive metal. During discharge the solvent is electrochemically reduced on a cathode current collector.
In electrochemical cells of the foregoing type of cylindrical configuration one form of electrode structure which has become widely used is the so-called "jelly-roll" type of electrode assembly which is described in U.S. Pat. Nos. 3,510,353 to McHenry and 4,020,248 to Goebel. With this type of electrode construction the anode electrode and the cathode current collector electrode are elongated structures which are wound in a coil to provide alternating anode and cathode current collector electrodes separated by intervening insulating material. The cylindrical battery stack thus formed is placed in a cylindrical case of a housing with appropriate electrical connections provided between the electrodes and external terminals.
Cells with the foregoing "jelly-roll" battery stack arrangement may exhibit certain problems, particularly when operated under high discharge conditions. The paths of current flow from different portions of each of the electrodes to the external terminals vary; and, therefore, internal temperatures and internal resistances are not uniform throughout the battery stack. With electrodes of large area for operation under high discharge conditions current paths from some portions of the electrodes are relatively long causing excessive internal resistance losses. There are also difficulties in winding the assembly of electrodes and in assembling the battery stack with the cylindrical case of the cell housing.